a. Field of the Invention
The present invention relates generally to orthotic devices for use in shoes, and, more particularly, to an orthotic insert having a heel post with an angled lower surface of the lateral side for controlling angulation in a lateral direction at heel strike and a rigid plate member with a distal medial portion for controlling angulation in a medial direction as the foot progresses towards toe-off.
b. Related Art
Orthotic inserts have long been employed to treat conditions or otherwise enhance the functions of the human foot, whether for ordinary walking or for various forms of specialized activities, such as skiing, skating, running and so on.
A particular category of these devices employs a built-up structure in which there is a generally rigid, but still somewhat resilient flexible plate for supporting the plantar surface of the foot, and a thick, vertical post which is mounted to the heel end of the plate. Typically, the orthotic plate is constructed of a somewhat thin, generally rigid material, such as glass- or graphite-fiber/resin composite materials, polyurethane, molded plastics or the like. The post, in turn, is frequently formed of a generally hard but somewhat compressively yielding material, such as hard rubber, molded urethane, Neoprene or methyl methacrylate, which is capable of supporting the rear foot under the loads that are developed at heel strike.
Such devices are generally intended to both correctly position the foot at heel strike and control the motions of the foot as it progresses through the stance phase of the gait cycle from heel strike towards toe-off. The insert also provides or madates a range of motion in the joints of the foot. For example, a normal foot should roll (frontal plane motion) about 4xc2x0-6xc2x0 when walking. To control the motion of the foot, the plate member flexes resiliently to a controlled degree, and frequently there is also a need to impart a degree of rocking or eversion/inversion motion at the heel post as well, depending on the needs of the individual foot and the intended use. For example, it is often desirable to position the foot so as to increase inversion at heel contact, so as to increase the total amount of pronation and therefore the total amount of motion which is available for the balance of the gait cycle.
In order to provide the desired degree of inversion at heel strike, common practice in the prior art has been to form the heel post with a flat bottom that extends parallel to the transverse plane of the foot and insole. Material is then ground or otherwise removed from the bottom of the heel post on the lateral side. For example, FIG. 3 shows an exemplary prior art orthotic device 10 having a rigid plate 12 and raised heel post 14. A portion of the flat bottom surface 16 has been ground off to form an angled secondary surface 18 on the lateral side of the post. This provides the post with a xe2x80x9cbi-planarxe2x80x9d bottom which is intended to pivot the post through a controlled angle xcex80, from a first position in which the mean bottom surface 16 rests flat on the transverse plane 20, to a second position in which the upwardly-angled lateral surface 18 rests on the insole. The rocking motion of the heel post is imparted to the plate member 10 which is mounted to the top of the post, the plate member being the component which actually bears against and engages the plantar surface of the person""s foot. Thus, the post inverts the rearfoot at heel strike, when the weight is borne mostly on the lateral side of the heel, as indicated at 22 in FIG. 2. Then, as indicated by dotted line 24, the weight shifts forwardly and medially as the foot progresses through the gait cycle. As the weight shifts onto the medial side of the foot, as indicated at 26 in FIG. 2, the post is intended to pivot medially and return the device to the initial orientation shown in FIG. 3.
For several reasons, the operation of prior art devices of this type has frequently been unsatisfactory. For example, as can be seen in FIG. 4, the insole 30 and heel counter 32 of a conventional shoe are usually convexly curved in order to accommodate the heel. As a result, the edges of the bi-planar post tend to dig into and xe2x80x9chang upxe2x80x9d on the sides of the heel counter/insole, especially along the medial and lateral edges 34, 36. This impairs the ability of the post to produce the desired rocking motion, to the point that deep wear areas often develop where the edges of the post press into and rub against the material of the heel counter.
As can be seen in FIG. 4, the flat bottom 16 and the tendency of the edges to hang up on the sides of the counter/insole also tend to prevent the post from fitting all the way down into the shoe, so that a significant gap 38 is left between the insole and the bottom of the device. This causes the heel of the orthotic to sit excessively high in the heel of the shoe and creates user discomfort. Moreover, the unpredictable engagement between the post and counter/insole often causes the post to become tilted one way or another and out of proper alignment with respect to the transverse plane, so that even if the device is able to rock back and forth in the shoe it is unable to develop the desired angulation and range of motion.
Practitioners have resorted to various expediencies in an effort to address these problems. For example, it is common to attempt to xe2x80x9ccustom fitxe2x80x9d the device to the interior of the shoe by grinding away additional material along the perimeter of the post and/or gradually increasing the angle of the lateral plane until the desired degree of motion is achieved. However, this requires considerable tedious work, and unless great care is exercised too much material may be removed so that the device must be discarded. In other instances, practitioners have resorted to filling in the heel area of the insole in order to provide a raised, flat surface for the medial plane of the post, referred to as a xe2x80x9cheel raisexe2x80x9d but this is again an expensive and time-consuming process, and also modifies the shoe so that in some instances it can no longer be used without the orthotic insert.
Still further, even in installations where the device ends up functioning as intended, the results have often been less than ideal from a biomechanical standpoint. For example, employing the flat medial surface of the post to control the range of motion creates an abrupt stop to the rocking motion as the weight of the foot shifts to the medial side. This is quite noticeable and somewhat uncomfortable to the wearer, and also counteracts the normal shock-absorbing function of the foot as it pronates. In some instances designers have attempted to compensate for this problem by using a softer, more flexible material for the orthotic plate, however, the reduction in rigidity tends to compromise the structural integrity of the plate and its ability to properly support and control the motions of the foot. Moreover, the abrupt stop tends to cause the material of the plate to flex excessively in the area just forward of the distal medial edge of the post (see area 40 in FIG. 1); over time, the flexing causes the plate to develop cracks in this area, which is a principle cause of failure of orthotic inserts of this type.
Accordingly, there exists a need for an orthotic insert having a heel post, in which the heel post fits into the curved insole and heel counter of the shoe without impairing the desired pivoting motion of the insert. Furthermore, there exists a need for such an orthotic insert in which the bottom of the post fits down into the shoe without hanging up on the sides of the heel counter/insole, so that the insert does not sit excessively high within the shoe. Still further, there exists a need for such an orthotic insert which does not create an abrupt stop to the pivoting motion in the medial direction, as the weight of the foot is transferred to medial side of the insert, so as to provide enhanced shock-absorption characteristics and reduce structural damage to the rigid plate of the insert. Still further, there exists a need for such an orthotic insert having a heel post that can be manufactured and used in a standardized form, and that does not require expensive and time-consuming custom fitting for use in conventional shoes.
The present invention has solved the problems cited above, and is an orthotic insert for removable placement in shoe having an insole and a heel counter. Broadly, the orthotic insert comprises: (a) a substantially rigid plate member for engaging a plantar surface of a foot and having a heel end and a forefoot portion, the forefoot portion extending forwardly to at least proximal a metatarsal head area of the foot and having a distal medial portion for engaging the insole substantially along a transverse plane of the shoe, and (b) a heel post having an upper end mounted to a heel end of the plate member and a lower end extending downwardly therefrom, the lower end of the heel post comprising (i) a generally planar lateral bottom surface that extends upwardly and laterally at a predetermined angle for engaging the insole of the shoe so as to provide angular placement and limit pivoting motion of the heel post in the lateral direction, and (ii) a medial bottom surface that extends generally upwardly and medially for freely interfitting with the insole and heel counter so as to avoid the limiting pivoting motion of the heel post in the medial direction, so that the lateral bottom surface of the heel post engages the insole of the shoe so as to arrest pivoting motion of the orthotic insert in the lateral direction as weight is borne on a lateral side of the foot at heel strike, and the distal medial portion of the plate member engages the insole so as to arrest pivoting motion of the insert in the medial direction as weight is shifted to a medial side of a foot as the foot progresses through a gait cycle.
The lower end of the heel post may further comprise a generally planar central bottom surface intermediate the medial and lateral bottom surfaces that extends generally parallel to the transverse plane for engaging the insole so as to stabilize the orthotic insert within the shoe and provide a more gentle transition in the rolling motion.
The medial bottom surface of the heel post may comprise a generally planar medial bottom surface that extends upwardly and medially from the central bottom surface. The planar medial bottom surface and the planar lateral bottom surface may extend upwardly at approximately equal angles to the transverse plane.
The medial bottom surface of the heel post may have a generally convex contour for freely interfitting with the insole and heel counter. The generally convex contour may comprise a substantially continuous curved surface or one or more generally planar surfaces.
The distal medial portion of the rigid plate member may be located proximate a first metatarsal head of the foot. The distal medial portion of the plate member may comprise a forward edge portion of the plate member, and the forward edge of the rigid plate member may generally follow a line of metatarsal heads of the foot.
The present invention also provides a heel post for mounting to a substantially rigid plate member of an orthotic insert, the rigid plate member having a heel end and a forefoot portion extending to at least proximal a metatarsal head area of the foot and having a distal medial portion for engaging the insole of the shoe substantially along a transverse plane of the shoe. The heel post comprises (a) an upper end for being mounted to the heel end of the rigid plate member, and (b) a lower end for extending downwardly from the heel end of the rigid plate member, the lower end of the heel post comprising a generally planar lateral bottom surface that extends laterally and upwardly for engaging the insole so as to provide angular placement and limit pivoting motion of the heel post in a lateral direction, and a medial bottom surface that extends generally upwardly and medially for freely interfitting with the insole and heel counter so as to avoid limiting pivoting motion of the heel post in the medial direction.
The lower end of the heel post may further comprise a generally planar central bottom surface intermediate the medial and lateral surfaces that extends generally parallel to the transverse plane for engaging the insole so as to stabilize the orthotic insert within the shoe and provide a more gentle transition in the rolling motion.
The medial bottom surface of the heel post may comprise a generally planar medial bottom surface that extends upwardly and medially from the planar bottom surface. The generally planar medial bottom surface and the generally planar lateral bottom surface may extend upwardly at approximately equal angles to the transverse plane, and the upper end of the heel post may be configured for interchangeable mounting to rigid plate members for use with right and left feet.
The medial bottom surface of the heel post may have a generally convex contour for freely interfitting with the insole and heel counter of the shoe. The generally convex contour of the medial bottom surface of the heel post may comprise a substantially continuous curved surface, or may comprise one or more generally planar surfaces.
These and other features and advantages of the present invention will be apparent from a reading of the following detailed description with reference to the accompanying drawings.